The present invention relates generally to the field of medical diagnostic systems, such as imaging systems. More particularly, the invention relates to a system and technique for accurately and efficiently prescribing the geometry of a subsequent imaging volume of a structure of interest using at least two two-dimensional MR imaging sections as well as a system and technique for retrieving geometry information from a previously prescribed imaging volume and manipulating this geometry information.
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field Bo), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but process about it in random order at their characteristic Larmor frequency. If the substance, or tissue, is subjected to a magnetic field (excitation field B.sub.1) which is the x-y plane and which is near the Larmor frequency, the net aligned moment, M.sub.z, may be rotated, or "tipped", into the x-y plane to produce a net transverse magnetic moment M. A signal is emitted by the excited spins after the excitation signal B.sub.1 is terminated and this signal may be received and processed to form an image.
When utilizing these signals to produce images, magnetic field gradients (G.sub.x, G.sub.y and G.sub.z) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used. The resulting set of received NMR signals are digitized and processed to reconstruct the image using one of many well known reconstruction techniques.
When attempting to define the volume of coverage of an MR imaging scan, the NMR system operator may desire to quickly view a preview MR image (such as a real-time MR image) of the anatomical section within this volume of coverage. This process can be particularly useful when prescribing a three dimensional imaging volume, in which the desired high spatial resolution requires the thinnest slab possible. It is desirable to position this thin slab such that the anatomical section within the volume of coverage is complete, i.e. for example, covers the entire desired vascular network. Thus, a quick view of each side of the slab prior to initiating the three dimensional acquisition is useful for insuring that the entire anatomical section desired is within the defined volume of coverage.
Typically, two dimensional axial, sagittal and/or coronal "scout" images are first acquired. Such scout images are stored for later use. To use, the operator calls up the scout image and either graphically or explicitly (using geometry coordinates) prescribes the imaging volume directly on the scout images. The imaging volume may be either a two dimensional stack of slices or a three dimensional slab of the structure of interest. The drawback of this technique is that the operator does not actually see the results of the prescribed geometry until the subsequent imaging volume is acquired. Prescription errors cannot be detected nor corrected until the imaging volume acquisition is complete. Thus, when prescription errors exist, the operator is required to re-prescribe and re-acquire the imaging volume of the desired anatomical section.
Solutions to the problems described above have not heretofore included significant remote capabilities. In particular, communication networks, such as, the Internet or private networks, have not been used to provide remote services to such medical diagnostic systems. The advantages of remote services, such as, remote monitoring, remote system control, immediate file access from remote locations, remote file storage and archiving, remote resource pooling, remote recording, remote diagnostics, and remote high speed computations have not heretofore been employed to solve the problems discussed above.
Thus, there is a need for a medical diagnostic system which provides for the advantages of remote services and addresses the problems discussed above. In particular, there is a need for accurately and efficiently prescribing the geometry of a subsequent imaging volume of a structure of interest using at least two two-dimensional MR imaging sections over a network from a remote location. Further, there is a need for retrieving geometry information from a previously prescribed imaging volume and manipulating this geometry information over a network. Even further, there is a need for manipulation of MR imaging systems remotely via a network.